Straightening machine and method for the operation thereof

ABSTRACT

A straightening machine for straightening a metal strip or planar metal parts is provided, having a number of upper straightening rollers  15  which are each mounted at one first and one second bearing location  24, 25  in an upper roller mill  12 , and a number of lower straightening rollers  16  are each mounted at one first and one second bearing location  24, 25  in a lower roller mill  14 . The upper and lower straightening rollers  15, 16  are disposed such that they form a straightening gap  17  between an inlet  6  and an outlet  7  of the straightening machine  1  to act from above and from below on the metal strip or metal part  10  to be straightened and to guide the latter through the straightening machine  1 . The straightening rollers are provided with coupling elements  5 , disposed on an end side, for coupling drive shafts of a drive device  2, 3, 4 , and are removable from the respective roller mill  12, 14 . At least some of the straightening rollers  15, 16  are provided with coupling elements  5  at in each case both ends sides, so as to be able to reverse the straightening rollers  15, 16  within the roller mill  12, 14.

INCORPORATION BY REFERENCE

The following documents are incorporated herein by reference as if fully set forth: German Patent Application No. 10 2017 110 891.2, filed May 18, 2017.

BACKGROUND

The present invention relates to a straightening machine for straightening a metal strip or planar metal parts, and to a method for operating such a straightening machine.

Such straightening machines comprise a number of upper straightening rollers which are mounted in an upper roller mill, and a number of lower straightening rollers which are mounted in a lower roller mill. The upper and lower straightening rollers are disposed such that they form a straightening gap between an inlet and an outlet of the straightening machine, so as to therein act from above and from below on the metal strip or metal part to be straightened and to hereby guide the metal strip or metal part through the straightening machine. The straightening rollers at an end side are provided with coupling elements for coupling drive shafts, in most instances articulated shafts, of a drive device. Finally, the straightening rollers are removable from the respective roller mill such that they can be replaced upon reaching a wear limit.

Straightening machines of the present type serve for removing stresses and unevenness in metal strips or metal parts. The upper and lower straightening rollers are disposed so as to be mutually offset along the straightening gap in such a manner that the material to be straightened is guided in a meandering manner through the straightening gap and thereby is bent in an alternating upward and downward manner on the straightening rollers. Bending is performed such that the material at least on the first straightening rollers is bent beyond the tensile yield point of said material, such that undesirable bends and stresses in the material are removed as completely as possible. The material is usually heavily plasticized on the first straightening roller of the straightening machine. The material is bent to a slightly lesser extent on each further straightening roller, and the material is no longer plasticized, that is to say is only elastically deformed, on the last straightening roller.

Metal strips which are supplied as so-called coils and are unwound therefrom for production are often used in the metal-processing industry. Unevenness and stresses in the strip material which are unfavorable for further processing are created by winding the strip material into coils, but also by any potential prior thermal treatments and the like. Therefore, metal strips, after being unwound from the coil, are typically directed through the straightening gap of a straightening machine of the present type, said metal strips exiting said straightening gap in a flat and unstressed manner.

However, this is not the only application, since planar metal parts which are to be relieved of undesired bends and stresses are also typically straightened in a straightening machine of the present type, in order for said planar metal parts to be able to be processed further. Great advantages are provided by way of the present invention in particular in the case of such part straightening machines.

A straightening machine of the type mentioned at the outset is known, for example, from EP-A-2 712 687. This known straightening machine is likewise particularly suitable for straightening planar metal parts and addresses the issue that the straightening gap of the straightening machine widens during a straightening procedure when the connection between the upper and the lower roller mill is assumed by stay bolts. According to this prior art, it is provided that the stay bolts are provided with adjustment devices for modifying the effective length of said stay bolts, such that changes in the effective length of the stay bolts in operation, typically elongations under load, can be compensated for in real time.

Further straightening machines of the present type are known, for example, from EP-A-2 002 907, relating in particular to a gear assembly for the straightening machine, and from EP-A-1 491 270.

The straightening rollers of a straightening machine of the present type usually have a coupling element at an end side for coupling articulated shafts of the drive device. Said coupling element is typically configured as a coupling spigot with an external profile. A bearing journal for an axial bearing is located on the opposite end side of the straightening rollers in the respective roller mill. In order for the straightening roller to be retrieved from the roller mill, the articulated shaft is pulled off the straightening roller on the drive side, the associated bearing location is released, and the straightening roller is pulled out of the opposite bearing location.

The straightening rollers of a straightening machine of the present type are exposed to high forces and accordingly are subjected to more or less rapid wear. The straightening rollers have to be replaced when the straightening rollers have reached a degree of wear which leaves behind visible faults on the surface of the metal strips or metal parts to be straightened. By virtue of the required high stability, strength, and dimensional accuracy of the straightening rollers, a replacement of the straightening rollers is correspondingly cost-intensive.

SUMMARY

The present invention is therefore based on the object of providing a straightening machine of the type mentioned at the outset and a method for operating said straightening machine, by way of which the service life of the straightening rollers can be increased in particular when the straightening machine is also used for straightening planar metal parts.

This object is achieved by a straightening machine and by a method having one or more features of the invention. Preferred design embodiments of the straightening machine according to the invention are described below and in the claims; advantageous refinements of the method according to the invention are also described below and in the claims.

It has been recognized according to the invention that straightening rollers of straightening machines which are used for straightening planar metal parts wear particularly rapidly on that side of the straightening machine which is opposite the drive device. This is associated with the fact that a person who operates the straightening machine and feeds the metal parts to be straightened into the inlet of the straightening machine, in that said person usually places said metal parts onto a roller track or another conveying installation that is disposed ahead of the inlet, for this purpose stands on that side of the straightening machine that is opposite the drive device. As a natural consequence thereof, the metal parts to be straightened, when the latter are narrower than the width of the inlet, will typically make their way into the straightening gap not in a centered manner but close to the operator, thus on that side of the straightening machine that faces away from the drive device. This leads to the straightening rollers on the operator side of the straightening machine wearing more rapidly than on the drive side.

It has furthermore been recognized according to the invention that in the case of such an asymmetrical load on the straightening rollers and of the substantially one-sided wear on said straightening rollers associated therewith, the service life of the straightening rollers can be quite simply significantly increased in that the straightening rollers are reversed within the straightening machine, that is to say are removed from the respective roller mill after a number of performed straightening procedures, reversed, and by way of swapped end sides reinserted into the roller mill.

In order for this to be enabled, it is provided according to the invention that the straightening rollers which are to be reversed are not only provided with coupling elements on one end side, as is the case in the prior art, but have coupling elements at in each case both end sides.

As is usual in the prior art, the coupling elements can be designed as profiled drive studs having a profiled cross section for the axial transmission of torque by a plug-fittable drive shaft or articulated shaft, respectively; it can alternatively be provided that the coupling elements are designed as drive sockets having a profiled cross section into which drive studs of drive shafts that are correspondingly profiled can be plugged. It is a common factor of both alternatives that the coupling and uncoupling of the straightening rollers thus configured from the drive shafts of a drive device can be performed by an axial movement.

A significantly improved service life of the straightening rollers can be achieved due to the reversible design embodiment of the straightening rollers according to the invention, wherein the improvement is greater the more often metal parts are straightened which run into the straightening gap in an eccentric manner, typically so as to be displaced toward the operator side of the straightening machine. By way of a reversal of the straightening rollers according to a schedule, the more heavily stressed and thus more rapidly wearing regions of the straightening roller are indeed swapped for the less stressed and thus less worn regions of the straightening roller. In the ideal case, a substantially uniform stress on the straightening rollers thus results.

In order for the service life of the reversible straightening rollers to be further increased, it is preferable in the context of the present invention for the straightening rollers to not only be reversed according to a schedule and by way of swapped end sides reinserted into the roller mill, but also for the sequence of the straightening rollers along the straightening gap to be swapped according to a schedule. It has indeed been recognized that the straightening rollers in the straightening procedure are all the more stressed and accordingly wear more intensely closer the said straightening rollers are disposed to the inlet of the straightening machine. If the sequence of the straightening rollers between the inlet and the outlet of the straightening machine is regularly reversed, the effect that more heavily stressed straightening rollers are swapped for less stressed straightening rollers in turn results, such that as a result all straightening rollers are stressed in a substantially uniform manner and wear in a uniform manner.

As is known per se from the prior art, it is also preferable in the case of a straightening machine according to the invention for each straightening roller on that side thereof that faces away from the straightening gap to be assigned at least two support roller pairs which support the straightening rollers against flexing in the straightening procedure.

It is a fact of nature that higher stress of the straightening roller arises herein in the contact regions between the support rollers and the straightening rollers, this above all leading to increased wear on the end-side edges of the support rollers. In the context of the present invention, it is therefore preferable for the support roller pairs for in each case one straightening roller to be disposed in such a manner that said support roller pairs are not positioned symmetrically in relation to a center of an imaginary line between the two bearing locations of the straightening roller. This leads to the contact regions between the support rollers and the straightening roller after the reversal of the straightening roller being located at another location of the straightening roller such that to this extent any premature wear in these contact regions and in particular in the region of the end-side edges of the support rollers is also avoided. This also further increases the service life of the straightening rollers.

In order for the schedule for the reversal of the straightening rollers according to the invention to be adapted in a manner that is as optimal as possible to the individual stress of the straightening machine and the straightening rollers thereof, it is preferable in the context of the method according to the invention for the forces which act in a straightening procedure between the upper and the lower roller mill, and the temporal profile thereof, to be detected and added up. This can be performed in a purely quantitative manner, in that whenever the value of a force that wishes to remove the upper roller mill from the lower roller mill lies above a specific threshold value, and at the same time the time interval in which the force lies above the threshold force exceeds a predefined minimum period, a counter which represents a completed straightening cycle is activated. Of course, however, it is also possible for the forces and/or the temporal profile thereof to be detected in a qualitative manner and for a load, which in the case of the detected straightening procedure has acted on the straightening machine, to be computed by way of correspondingly integrating said load. This load is accordingly a measure for the stress and indirectly thus for the wear to be expected on account of the respective straightening cycle, said load having a lower value when, for example, the time interval of the action of force is shorter than in the case of a straightening procedure having a longer time interval, for example because metal parts of dissimilar length have been straightened which otherwise have the same dimensions and are composed of the same material, or said load having a higher value so as to correspond to a detected asymmetry of the forces.

Preferably, individual values of forces which in the straightening machine act simultaneously between the two roller mills at different locations within the straightening machine are additionally measured, that is to say that the asymmetrical distribution of the forces, in as far as the latter are present, is preferably also detected. This can also be performed in a purely quantitative manner, in that it is counted when threshold values for a respective asymmetry of the forces and for a time interval in which said asymmetry lies above the threshold values are exceeded. However, a better approximation to the actual wear-causing procedures will be achieved when any possible asymmetrical distribution of the forces and the temporal profile of the latter is detected in a quantitative manner and optionally added up.

According to the invention, an expectancy value for wear of the straightening rollers is determined from the forces which are detected in a quantitative and/or qualitative manner and which act in a straightening procedure between the upper and the lower roller mill, from the temporal profile of said forces, and optionally from the asymmetrical distribution of said forces, and the straightening rollers, after reaching a predefined expectancy threshold value, are retrieved from the respective roller mill, reversed, and by way of swapped end sides, and optionally also by way of a reversed sequence, reinserted along the straightening gap into the roller mill. A balance between the desired and as uniform as possible wear of the straightening rollers and the frequency of the reversal procedure, the latter being associated with machine downtime, has to be found herein.

In order for the straightening machine according to the invention to be able to be operated by the method described above, sensors are preferably provided for detecting forces which act in the straightening procedure between the upper and the lower roller mill. This detection of forces can in turn be performed in a quantitative and/or qualitative manner. The sensors herein are preferably distributed in the straightening machine in order for, in addition to the detection of the forces acting in the straightening procedure between the upper and the lower roller mill, an asymmetrical distribution of said forces to also be detected in a quantitative and/or qualitative manner.

As is known per se, in the case of straightening machines which have stay bolts for connecting the upper and lower roller mills, the elongation of said stay bolts in the straightening procedure being compensated for by a modification of the effective length of said stay bolts, the stay bolts are typically provided with sensors, in particular displacement sensors, which detect an elongation of the respective stay bolts. It is therefore advantageous in the context of the present invention for the sensors for detecting the forces acting between the roller mills, and optionally the asymmetrical distribution of said forces, to be specifically those sensors which detect an elongation of the respective stay bolts and are configured, for example, as displacement sensors.

The sensors of the straightening machine according to the invention which detect, in a quantitative and/or qualitative manner, in the forces which act in the straightening procedure between the upper and the lower roller mill, the temporal profile of said forces and/or the asymmetrical distribution of said forces, are preferably assigned a load spectrum memory. Said load spectrum memory serves for storing detected forces and/or for storing and adding up straightening cycles that are determined in a quantitative or qualitative manner from the detected forces.

Alternatively or additionally, the load spectrum memory can be configured such that it stores the forces detected in a straightening procedure and the temporal profile of said forces and, in as far as detected, the asymmetrical distribution of said forces, and/or from the above in each case computes a load and optionally the asymmetrical distribution of said load, and stores the computed value as a load cycle. Said load cycles are a measure for the wear-generating stress of the straightening rollers, wherein optionally an asymmetrical distribution is incorporated in a weighted manner in the load cycles, such that an addition of the load cycles, this being able to be performed in the load spectrum memory, enables the wear that is generated by the load to be estimated.

There are a plurality of straightens of accuracy herein; pure counting of stresses above a stress threshold, this leading to a specific number of straightening cycles which are added up in the load spectrum memory, already permits a rough estimation of the wear of the straightening rollers that is caused by the straightening procedures, while a qualitative detection of the stress by way of a quantitative detection and evaluation of the forces acting in a localized manner, and of the temporal profile of said forces, for computing load cycles which are added up in the load spectrum memory reproduces the actual conditions pertaining to the wear of the straightening rollers in a more precise manner.

In any case, it is preferable for the straightening machine according to the invention to be provided with a wear computer which is configured in such a manner that it, from the straightening cycles or load cycles added up in the load spectrum memory, computes a wear value and emits a signal for reversing the straightening rollers when a predefined wear threshold value is reached. Alternatively, the wear computer, so as to be closer to the actual conditions, can be configured in such a manner that it, by the forces detected by the sensors and stored in the load spectrum memory, and the temporal profile of said forces and, when detected, the spatial distribution of said forces, computes an expectancy value for wear of the straightening rollers and emits a signal when a predefined expectancy threshold value is reached. The intermediate step of adding up the straightening cycles or the load cycles, respectively, can be dispensed with in the latter case.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of a straightening machine designed according to the invention will be described and explained in more detail hereunder by means of the drawings, in which:

FIG. 1 shows a schematic plan view from above of a straightening machine of the present type;

FIG. 2 shows a schematic front view of a straightening machine designed according to the invention;

FIG. 3 shows detailed views of the end sides of a straightening roller according to the prior art;

FIG. 4 shows a bearing location of a straightening roller according to the prior art;

FIG. 5 shows a bearing location of a straightening roller in a straightening machine designed according to the invention; and

FIG. 6 shows a schematic illustration of straightening rollers having associated support rollers.

DETAILED DESCRIPTION

A plan view of a straightening machine of the present type is illustrated in FIG. 1. The actual straightening machine 1, in which the straightening rollers (not visible here) are mounted, is provided on a drive side that here is illustrated on the right with a drive device which is composed of a drive motor 2 and of a gearbox block 3 and of a number of articulated shafts 4, the latter connecting the individual gearbox outputs to coupling elements 5 of the straightening rollers.

An inlet 6 and an outlet 7 of the straightening machine are provided with an inlet roller track 8 and an outlet roller track 9, respectively, so as to feed planar metal parts 10 into the inlet 6 or to retrieve said straightened planar metal parts 10 from the outlet 7, respectively.

Only a frame 11 and an upper roller mill 12 and adjustment devices 13 for stay bolts (not visible here) of the actual straightening machine 1 can be seen. The illustration in FIG. 1 highlights the set of issues in the case of part straightening machines which triggered the insights according to the invention and ultimately led to the present invention.

The operator indicated in FIG. 1 has the task of feeding the metal part 10 to be straightened into the inlet 6 and of retrieving said metal part 10 from the outlet 7 after the straightening procedure. To this end, said operator places the metal part 10, as is illustrated in FIG. 1, naturally onto the inlet roller track 8 such that said metal part 10 comes to lie close to the operator side, thus the side of the straightening machine 1 that in FIG. 1 is illustrated on the left. When the straightening machine 1, as in the present example, has a wide inlet 6, there are in operation quite often metal parts 10 of which the width does not correspond to the width of the inlet 6. Said metal parts 10 are then placed onto the inlet roller track 8 so as to be displaced in an eccentric manner toward the operator side, as is illustrated in FIG. 1. Accordingly, the straightening rollers of the straightening machine 1 in the straightening of the metal part 10 are stressed only in the regions that are oriented toward the operator side, while the regions of the straightening rollers that are oriented toward the drive side (illustrated on the right in FIG. 1) remain entirely unstressed by said straightening procedure.

FIG. 2 shows a schematic lateral view of the straightening machine 1 from FIG. 1, viewed from the operator side. An upper roller mill 12 and a lower roller mill 14 are mounted in the frame 11, wherein the two roller mills 12, 14 are interconnected by way of four stay bolts 20.

Presently, nine upper straightening rollers 15 are mounted in the upper roller mill 12, while, presently, ten lower straightening rollers 16 are mounted in the lower roller mill 14. The upper and lower straightening rollers 15, 16 are in each case disposed sequentially in a row in such a manner that said straightening rollers 15, 16, between the row of the upper straightening rollers 15 and the row of the lower straightening rollers 16, form a straightening gap 17 which extends through the straightening machine 1 from the inlet 6 to the outlet 7. If a metal part is now fed into the inlet 6, said metal part 10 is transported in the straightening gap 17 between the upper straightening rollers 15 and the lower straightening rollers 16 through the straightening machine 1 and herein is bent in an alternating upward and downward manner in a meandering line about the upper and lower straightening rollers 15, 16. For this purpose, the straightening rollers 15, 16 are disposed so as to be offset on the straightening gap 17.

The stay bolts 20 which connect the lower roller mill 14 to the upper roller mill 12 are fixedly anchored by means of anchor points 18 in the lower roller mill, while said stay bolts 20 are adjustably fastened to the upper roller mill 12. The adjustment devices 13 can be seen in FIG. 1; said adjustment devices 13 are fixedly connected to the upper roller mill 12 on the one hand, and on the other hand support a counter bearing for the stay bolts 20. The height of the counter bearing in relation to the upper roller mill can be modified by means of the adjustment devices 13 such that an elongation of the stay bolts 20 during a straightening procedure, in which the straightening gap 17 is widened by a metal part, can be compensated for by repositioning of the counter bearing in an upward manner, in that the mounting of the stay bolts 20 on the upper roller mill 12 is also “elongated” in a corresponding manner. To this extent, the adjustment device 13 does not modify the actual length of the stay bolts 20, but only the effective length of the latter that is proportional to the straightening gap 17, thus being able to keep the straightening gap 17 constant.

The flux of force of the counter forces in the passage of a metal part 10 through the straightening gap 17 runs from the upper roller mill 12 by way of the stay bolts 20 into the lower roller mill 14. The stay bolts 20 are elongated herein, wherein the elongation is all the more pronounced the less complex the stay bolts 20 are configured. The straightening gap 17 is widened on account of the elongation of the stay bolts 20, this however been compensated for by the adjustment device 13.

In order for such a compensation to be carried out in real time and for the straightening gap 17 to be kept constant, sensors 19 are attached to all four stay bolts 20, said sensors 19 presently being configured as displacement sensors. By virtue of the values for an elongation of the stay bolts 20 that are reported by the sensors 19 to a machine controller, the adjustment device 13 can increase the height of the counter bearing of the stay bolts 20 on the upper roller mill 12 in a corresponding manner such that the effective length of the stay bolts 20, despite an elongation of the latter, is not modified and the straightening gap 17 thus remains constant, that is to say is not widened. This design embodiment of a straightening machine is known per se from EP-A-2 712 687.

According to the invention, the sensors 19, which are anyway present as displacement sensors for the adjustment device 13, can now moreover be used to detect forces which act in a straightening procedure between the upper roller mill 12 and the lower roller mill 14, specifically in a localized manner at all four corners of the roller mills 12, 14, namely on each stay bolt 20.

Thus, by means of the values which are supplied by the sensors 19, conclusions can be drawn pertaining to forces which prevail in the straightening gap 17, and the temporal profile of said forces, at least the time interval in which said forces act, can be detected and optionally a conclusion can also be drawn pertaining to an asymmetrical distribution of the forces.

Depending on the desired accuracy, a conclusion can be drawn in various variants from the values supplied by the sensors 19 pertaining to the wear of the straightening rollers 15, 16.

For example, performed straightening cycles can be counted, wherein a straightening cycle is counted when a specific force is exceeded in the straightening gap 17, or in the present example a specific path of the sensors 19 for the elongation of the stay bolts 20 is exceeded for the duration of a specific time interval, respectively. Or a number of asymmetrical straightening cycles are counted, the latter being accordingly defined in that a specific asymmetry of sensor values beyond a specific threshold and beyond a predefined time interval is detected.

If the added number of straightening cycles and/or the added number of asymmetrical straightening cycles becomes so large that a predefined threshold value is achieved, a signal on the controller of the straightening machine 1 is emitted, said signal indicating that the straightening rollers 15, 16 are to be reversed and/or in terms of the sequence thereof along the straightening gap 17 are to be swapped, so as to achieve a uniform wear of all the straightening rollers 15, 16.

However, from values measured in a localized and temporal manner for the forces acting in the straightening gap, a conclusion can also be drawn pertaining to a magnitude of an asymmetrical wear of the straightening rollers 15, 16, and this magnitude can be used as a trigger for a signal for reversing and/or swapping the straightening rollers 15, 16.

In order for the straightening rollers 15, 16 to be able to be reversed, said straightening rollers 15, 16 according to the invention are provided with coupling elements 5 on both end sides. This is highlighted by FIG. 3, which shows the two end sides of a straightening roller 15 according to the prior art. According to the prior art, the straightening roller 15 has a coupling element 5 only at one end side thereof which presently is configured as a drive spigot having a profiled cross section for the axial transmission of torque. The straightening roller 15 according to the prior art at the other end side has a bearing journal 21.

As is shown in FIG. 4, the straightening roller 15 according to the prior art by means of said bearing journal 21 is mounted in a conventional axial bearing 22 in the associated roller mill 12.

In order for the reversibility of the straightening rollers 15, 16 according to the invention to now be enabled, said straightening rollers 15, 16 are provided with coupling elements 5 at both end sides, this necessitating a modification of the mounting of the straightening rollers 15, 16 in the roller mills 12, 14 thereof, as is illustrated in FIG. 5. The axial bearing 22, which in the prior art is disposed on an external side of the roller mill 12, has had to be repositioned to the internal side of the roller mill 12, or 14, respectively, as is illustrated in FIG. 5.

FIG. 6 finally shows in a schematic illustration a row of lower straightening rollers 16 and two pairs of associated support rollers 23 a and 23 b. The straightening roller 16 by means of the support rollers 23 a, 23 b are supported in relation to the straightening pressure in the roller mill 14 such that the entire straightening pressure is not dissipated by way of the first bearing locations 24 and the second bearing locations 24, on the one hand, and flexing of the straightening rollers 16 is avoided, on the other hand.

According to one preferred design embodiment of the present invention, the support roller pairs 23 a, 23 b in the case of this exemplary embodiment are not positioned symmetrically in relation to a center of an imaginary line which connects the two bearing locations 24, 25 of the straightening rollers 16, but are in each case displaced somewhat to the left. Therefore, the track of the support roller pairs 23 a, 23 b, by way of a reversal of the straightening rollers 16, is then located in another region of the straightening rollers 16, or is somewhat offset, respectively, such that a homogenization of the wear generated by the contact between the support rollers 23 and the straightening rollers 16 also takes place here.

In the present exemplary embodiment, a straightening machine 1 which is known per se from the prior art is therefore used and according to the invention is modified in that the straightening rollers 16, 17 are provided with coupling elements 5 at in each case both end sides. The sensors 19, which are present anyway, can then be used for carrying out the method according to the invention. In the simplest case, this is performed in that it is identified by way of dissimilar expansions of the four stay bolts 20, as reported by the sensors 19, that a metal part 10 has been fed eccentrically into the inlet 6 of the straightening machine 1, such that the straightening rollers 15, 16 are asymmetrically stressed. These straightening cycles that are identified as asymmetrical are added up in a load spectrum memory. As soon as the sum reaches a predefined threshold value, the straightening rollers 15, 16 are reversed, or a signal is emitted that is intended to initiate such a reversal, respectively.

However, since the sensors 19 are capable of supplying values which are proportional to the forces acting in a localized and temporal manner in the straightening gap 17, more exact load values for the wear-related stress of the straightening rollers 15, 16 can also be computed from these values and optionally be weighted using asymmetries, and be stored and added collectively as load cycles. A wear value can be computed from the load values, or selectively from the load cycle sums, and a signal for reversing and/or swapping the straightening rollers 15, 16 can be emitted when a predefined wear threshold value is reached. 

1. A straightening machine for straightening a metal strip or planar metal parts (10), the straightening machine comprising: a plurality of upper straightening rollers (15) mounted in an upper roller mill (12); a plurality of lower straightening rollers (16) mounted in a lower roller mill (14); the upper and lower straightening rollers (15, 16) being disposed to form a straightening gap (17) between an inlet (6) and an outlet (7) of the straightening machine (1) and are adapted to act from above and from below on the metal strip or metal part (10) to be straightened and to guide the metal strip or metal part through the straightening machine (1); the straightening rollers (15, 16) are provided with coupling elements (5) on a first end side thereof for coupling to drive shafts of a drive device (2, 3, 4), the straightening rollers (15, 16) are removable from the respective roller mill (12, 14); and at least some of the straightening rollers (15, 16) are provided with additional coupling elements (5) on a second end side opposite to the first end side.
 2. The straightening machine as claimed in claim 1, wherein the coupling elements (5) of the straightening rollers (15, 16) are configured as drive studs or drive sockets having a profiled cross section for axial transmission of torque.
 3. The straightening machine as claimed in claim 1, wherein each said straightening roller (15, 16) on the end side thereof that faces away from the straightening gap (17) is assigned at least two support roller pairs (23) which are positioned asymmetrically in relation to a center of an imaginary line that connects a first bearing location (24) and a second bearing location (25) of the straightening roller (15, 16).
 4. The straightening machine as claimed in claim 1, further comprising sensors (19) that detect forces which act in a straightening procedure between the upper and the lower roller mill (12, 14).
 5. The straightening machine as claimed in claim 4, wherein the sensors (19) are distributed in the straightening machine (1) in order to detect an asymmetrical distribution of said forces.
 6. The straightening machine as claimed in claim 4, further comprising stay bolts (20) that interconnect the upper and the lower roller mill (12, 14), and at least some of the stay bolts (20) are provided with the sensors (19) that detect an elongation of the respective stay bolts (20).
 7. The straightening machine as claimed in claim 6, wherein the sensors (19) are displacement sensors.
 8. The straightening machine as claimed in claim 4, further comprising a load spectrum memory assigned to the sensors (19) configured to at least one of store detected forces or store and add up straightening cycles that are determined from the detected forces.
 9. The straightening machine as claimed in claim 8, wherein the load spectrum memory is configured such that it stores the forces detected in a straightening procedure and a temporal profile of said forces and, when detected, an asymmetrical distribution of said forces, or in each case computes a load and, when detected, an asymmetrical distribution of the load from the forces detected in a straightening procedure and from the temporal profile of said forces, stores the latter as a load cycle, and adds up the load cycles.
 10. The straightening machine as claimed in claim 9, wherein the straightening machine (1) further comprises a computer configured to detect wear from the straightening cycles or load cycles added up in the load spectrum memory, and computes a wear value and emits a signal when a predefined wear threshold value is reached.
 11. The straightening machine as claimed in claim 9, wherein the straightening machine (1) further comprises a computer which is configured to detect wear from the forces detected by the sensors (19) and stored in the load spectrum memory, and the temporal profile of said forces and, when detected, a spatial distribution of said forces, computes an expectancy value for wear of the straightening rollers (15, 16) and emits a signal when a predefined expectancy threshold value is reached.
 12. A method for operating a straightening machine (1) as claimed in claim 1, the method comprising: removing the straightening rollers (15, 16) provided with the additional coupling elements (5) on the second end side after a number of performed straightening procedures, from the respective roller mill (12, 14), and reversing the straightening rollers (15, 16) provided with the additional coupling elements (5) on the second end side and reinserting the straightening rollers (15, 16) provided with additional coupling elements (5) on the second end side into the roller mill (12, 14).
 13. The method as claimed in claim 12, further comprising: detecting at least one of forces that act between the upper and the lower roller mill (12, 14) in a straightening procedure, or the asymmetry of said forces, counting the performed straightening procedures as straightening cycles, and carrying out the removing and the reversing of the straightening rollers (15, 16) after reaching a predefined straightening cycle threshold value for a number of the performed straightening procedures.
 14. The method as claimed in claim 12, further comprising: detecting and adding up forces that act between the upper and the lower roller mill (12, 14) in a straightening procedure to form a temporal profile of said forces and, when detected, an asymmetrical distribution of said forces, determining an expectancy value for wear of the straightening rollers (15, 16), and after reaching a predefined expectancy threshold value, carrying out the removing and the reversing of the straightening rollers (15, 16) provided with the additional coupling elements (5) on the second end side.
 15. The method as claimed in claim 14, further comprising; in addition to carrying out the reversing of the straightening rollers (15, 16), reversing a sequence of the straightening rollers (15, 16) along the straightening gap (17). 